Harry Brook scored England's first triple century since 1990 on a record-breaking fourth day against Pakistan, with the tourists smashing 823 before embarking on a stirring victory push in the First Test.

England's 'Bazball' bravado ran wild in Multan as they piled up the fourth-highest total ever seen in Test cricket, declaring seven down after Brook and Joe Root made history with a partnership of 454 runs.

Brook finished with a staggering 317 from 322 balls, terrain not seen since Graham Gooch's 333 against India 34 years ago, and Root celebrated overtaking Sir Alastair Cook as the country's leading run-scorer on Wednesday with a career-best 262.

A shellshocked Pakistan then faltered to 59 for five before closing on 152 for six - still behind by 115.

Brook's effort took him fifth on England's all-time list but the monster stand he shared with Root easily eclipsed the previous best of 411 between Peter May and Colin Cowdrey, against the West Indies in 1957.

Only three pairings globally have ever put on more than the Yorkshire duo and they made sure to leapfrog Australian great Sir Donald Bradman's highest-ever partnership by three runs before giving way.

The gargantuan score and statistical barrage that came with it would have been sweet enough for England, who conceded 556 in the first innings and somehow flipped that into a lead of 267, but it became even better as Pakistani wickets began to tumble.

There were signs that England's merciless scoring had broken the home side's spirit - the dejected looking bowlers, lethargic ground fielding, the truly terrible catching - but it took a top-order implosion to confirm they had lost their heart for the fight.

After 150 demoralising overs of chasing leather with diminishing returns, 86.3 of which were spent trying to part Root and Brook, they lost opener Abdullah Shafique to the very first ball of their second innings.

It was a fine piece of skill from Chris Woakes, nipping in and sending off stump spiralling, but the sense of disbelief was tangible. First-innings centurion Shan Masood survived two drops before chipping Gus Atkinson to short mid-wicket for 11 and the Surrey seamer had Babar Azam caught behind moments later with a delivery that nipped away.

Debutant Brydon Carse, who had the honour of taking England past the 800 mark by clubbing his second ball as a Test batter for six, then joined the fun. He took out Saim Ayub with his loosener, well caught by the retreating Ben Duckett at mid-off, and bowled the off-form Mohammad Rizwan through a gaping defence.

After just 13 wickets had fallen in the first 10 sessions of the match, Pakistan conspired to lose five in 12.1 overs. Jack Leach made it six when he had Saud Shakeel caught behind but a four-day win slipped through Shoaib Bashir's fingers as he dropped Aamer Jamal at fine-leg to deny the impressive Carse.

Pakistan took the field without spinner Abrar Ahmed, reportedly hospitalised with fever, and despite holding a lead of 64 at the start of play quickly looked like passengers in the Root and Brook show.

They put on 166 runs in 29 overs in the morning, toying with the gaps in the field and making light of negative leg-side bowling lines to keep the scoreboard rolling along at speed. Root was badly dropped at midwicket on 186 by Babar, whose sloppiness cost 73 runs, and Jamie Smith was later put down twice in a late cameo as heads dropped.

The landmark moments were ticked off, Root reaching 200 for the sixth time in his career and accelerating past 250 with a reverse scoop. Brook ticked off his Test best of 186, his first-class best of 194 and made his double ton in 245 balls.

He brought up the 400-run partnership with a cheeky uppercut for four and, after being interrupted lunch, ended May and Cowdrey's 67-year record in the first over of the afternoon. Brook played with complete control, dropping to his knees to ramp the spinners, picking the gaps with impunity and scoring singles at will.

Root finally gave way after 10 hours at the crease when he was lbw to Agha Salman but Brook delved into waters even his masterful team-mate has never stepped. He became just the sixth Englishman to reach 300, raising his bat skywards in honour of his late grandmother Pauline.

By now he seemed less engaged in a battle with Pakistan and more with Sir Len Hutton's England record of 364. At the rate he was going, 99 runs off 65 balls after the break, it would not have taken him long to get there. But a top-edged sweep brought him up short and, like Root, he was mobbed with handshakes by the opposition as a mark of respect on his way to the pavilion.

His efforts had knocked the stuffing out of Pakistan, who will need to mount a serious fightback to avert a final day defeat.